US7761005B2 - Relay finder optical system of an single-lens reflex camera - Google Patents
Relay finder optical system of an single-lens reflex camera Download PDFInfo
- Publication number
- US7761005B2 US7761005B2 US12/050,328 US5032808A US7761005B2 US 7761005 B2 US7761005 B2 US 7761005B2 US 5032808 A US5032808 A US 5032808A US 7761005 B2 US7761005 B2 US 7761005B2
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- US
- United States
- Prior art keywords
- lens group
- positive
- optical system
- relay
- lens
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related, expires
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Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B13/00—Viewfinders; Focusing aids for cameras; Means for focusing for cameras; Autofocus systems for cameras
- G03B13/02—Viewfinders
- G03B13/06—Viewfinders with lenses with or without reflectors
- G03B13/08—Viewfinders with lenses with or without reflectors with reflected image of frame
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
- G02B23/14—Viewfinders
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B25/00—Eyepieces; Magnifying glasses
- G02B25/001—Eyepieces
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B13/00—Viewfinders; Focusing aids for cameras; Means for focusing for cameras; Autofocus systems for cameras
- G03B13/18—Focusing aids
Definitions
- the present invention relates to a relay finder optical system of a single-lens reflex (SLR) camera.
- SLR single-lens reflex
- a finder optical system of an SLR camera has a fundamental structure in which an image formed on a primary imaging plane (focusing plate) through a photographing lens system is re-formed on a secondary imaging plane through a relay finder optical system, and the secondary image is viewed by the photographer through a Lupe (magnifying) optical system (an eyepiece optical system).
- a Lupe optical system an eyepiece optical system
- the size of the secondary imaging plane can be made smaller with respect to the size of the field-of-view frame. Consequently, such a smaller magnification of the relay finder optical system contributes to further miniaturization of the camera (finder optical system).
- the focal length of the Lupe (magnifying) optical system is inevitably made shorter; and as a result, the eye relief becomes shorter, the diameter of the Lupe (magnifying) optical system becomes larger, and the structure of the Lupe (magnifying) optical system is complicated.
- the present invention provides a relay finder optical system of an SLR camera, in which aberrations can be well corrected and further miniaturization can be achieved, while securing a necessary eye relief, an apparent visual angle, and a finder magnification.
- a relay finder optical system of a single-lens reflex camera, includes a condenser lens group, a prism, and a relay lens group, in this order from a primary imaging plane which is optically equivalent to an imaging plane of the single-lens reflex camera.
- An image which is formed on the primary imaging plane, and which is upside down and inverted from left to right, is re-formed on a secondary imaging plane for viewing by a photographer.
- the relay lens group includes a front lens group having a positive refractive power (hereinafter, a positive front lens group), an intermediate lens group having a negative refractive power (hereinafter, a negative intermediate lens group), and a rear lens group having a positive refractive power (hereinafter, a positive rear lens group), in this order from the object.
- a positive front lens group having a positive refractive power
- an intermediate lens group having a negative refractive power hereinafter, a negative intermediate lens group
- a rear lens group having a positive refractive power hereinafter, a positive rear lens group
- the most photographer's-eye side lens element of the positive rear lens group includes a positive lens element having a convex surface facing toward the eyes of a photographer, and satisfies the following conditions: 1 ⁇ SF (1) ⁇ 6 ⁇ f/fM ⁇ 3 (2)
- r 1 designates the radius of curvature of the object-side surface of the most photographer's-eye side positive lens element of the positive rear lens group
- r 2 designates the radius of curvature of the photographer's eye-side surface of the most photographer's-eye side positive lens element of the positive rear lens group;
- f designates the focal length of the relay finder optical system
- fM designates the focal length of the negative intermediate lens group.
- the positive rear lens group preferably includes three separate positive lens elements.
- the negative intermediate lens group preferably includes a negative biconcave single lens element.
- the positive front lens group preferably includes a positive single lens element.
- the relay finder optical system preferably satisfies the following condition: ⁇ 0.35 ⁇ m ⁇ 0.25 (3)
- m designates the transverse magnification of the relay finder optical system.
- FIG. 1 is a lens arrangement of the relay finder optical system, according to a first embodiment of the present invention
- FIGS. 2A , 2 B, 2 C and 2 D show aberrations occurred in the lens arrangement shown in FIG. 1 ;
- FIGS. 3A , 3 B, 3 C, 3 D, 3 E, 3 F, 3 G and 3 H show transverse aberrations (coma) occurred in the lens arrangement shown in FIG. 1 ;
- FIG. 4 is a lens arrangement of the relay finder optical system, according to a second embodiment of the present invention.
- FIGS. 5A , 5 B, 5 C and 5 D show aberrations occurred in the lens arrangement shown in FIG. 4 ;
- FIGS. 6A , 6 B, 6 C, 6 D, 6 E, 6 F, 6 G and 6 H show transverse aberrations (coma) occurred in the lens arrangement shown in FIG. 4 ;
- FIG. 7 is a lens arrangement of the relay finder optical system, according to a third embodiment of the present invention.
- FIGS. 8A , 8 B, 8 C and 8 D show aberrations occurred in the lens arrangement shown in FIG. 7 ;
- FIGS. 9A , 9 B, 9 C, 9 D, 9 E, 9 F, 9 G and 9 H show transverse aberrations (coma) occurred in the lens arrangement shown in FIG. 9 ;
- FIG. 10 shows the finder optical system of an SLR camera having the relay finder optical system according to the present invention.
- FIG. 10 shows the finder optical system of an SLR camera having the relay finder optical system according to the present invention.
- This SLR camera is provided with a photographing optical system 10 , a main mirror 11 supported by a mirror box 14 , a relay finder optical system 20 , a Lupe (magnifying) optical system 30 , and an imaging back 52 having an imaging device 51 installed behind the mirror box 14 .
- the main mirror 11 i.e., a quick return mirror as employed in a known SLR camera, is arranged to stay at a photography-standby position (position A), or flips up to a photography position (a position B).
- object-carrying light rays which are transmitted through the photographing optical system 10 , are reflected by the main mirror 11 and thereafter are guided to be incident upon a focusing plate (primary imaging plane) 12 which is optically equivalent to the imaging plane of the imaging device 51 (of the SLR camera).
- object-carrying light rays which are transmitted through the photographing optical system 10 , are incident on the imaging device 51 .
- the relay optical system 20 includes a condenser lens group 21 , a prism (trapezoidal prism) 22 , and a relay lens group 25 , in this order from the focusing plate 12 .
- the prism 22 has a first reflection surface 22 a , a second reflection surface 22 b and a third reflection surface 22 c ; and by these reflection surfaces, the object-carrying light rays, being through the photographing optical system 10 and forming an image on the focusing plate 12 , are guided to the relay lens group 25 .
- the image formed on the focusing plate 12 is upside down and inverted from left to right; and this inverted image is again inverted through the prism 22 and the relay lens group 25 to form an erect image, and the erect object image is re-formed on a secondary imaging plane 27 .
- the erect image formed on the secondary imaging plane 27 is magnified by and viewed through the Lupe (magnifying) optical system 30 .
- the present invention relates to the relay lens group 25 ; and therefore the relay lens groups 25 is explained in detail in the embodiments of the present invention.
- the arrangement of the condenser lens 21 , and those of the prism 22 and the eyepiece optical system 30 may have some degree of freedom on their (optical) design.
- the relay lens group 25 according to the present invention can be used with the condenser lens groups 21 with different specifications.
- the same can respectively be applied to the prisms 22 and to the Lupe (magnifying) optical systems, i.e., the relay lens group 25 can be used with the prisms 22 and the relay lens group 25 with their different specifications.
- the relay lens group 25 includes a positive front lens group 25 a , a negative intermediate lens group 25 b and a positive rear lens group 25 c , in this order from the object.
- the positive front lens group 25 a includes a positive single lens element
- the negative intermediate lens group 25 b includes a negative biconcave single lens element
- the positive rear lens group 25 c includes three separate positive lens elements.
- the positive front lens group 25 a can further miniaturize the relay finder optical system 20 , and is arranged to correct overcorrected spherical aberration and astigmatism which are occurred in the negative intermediate lens group 25 b.
- the negative intermediate lens group 25 b is arranged to correct field curvature and distortion.
- the positive rear lens group 25 c is arranged to attain telecentricity by converging the object-carrying light rays which has been diverged by the negative intermediate lens group 25 b , which also contributes to further miniaturize the relay finder optical system 20 .
- the lens element which satisfies condition (1) is a positive meniscus lens element having the convex surface facing toward the photographer's-eye.
- the positive meniscus lens element Since the shape of the positive meniscus lens element is similar to that of an aplanatic lens element, the positive meniscus lens element is effective for the correcting of distortion while the occurrence of spherical aberration and coma is reduced.
- the positive meniscus lens element satisfying condition (1) can attain telecentricity in the relay finder optical system 20 , and can effectively prevent a decrease of the amount of peripheral illumination.
- the principal point shifts toward the photographer's eye. Therefore the distance between the positive meniscus lens element and the secondary imaging plane 27 can be made longer. As a result, dust on a lens surface can be made less noticeable.
- peripheral edge of the positive meniscus lens element is positioned closer the object from the convex surface, a larger space is secured in the vicinity of the secondary imaging plane 27 , so that display components can easily be installed in the finder.
- Condition (2) specifies the focal length (refractive power) of the negative intermediate lens group 25 b .
- the negative intermediate lens group 25 b is arranged to correct field curvature and distortion; however, if the focal length thereof is too short, i.e., the refractive power thereof is too strong, the correcting of aberrations becomes difficult, since the balance of the refractive power among the negative intermediate lens group 25 b , the positive front lens group 25 a and the positive rear lens group 25 c is lost.
- the focal length of the negative intermediate lens group 25 b becomes longer, i.e., the refractive power thereof becomes weaker, to the extent that f/fM exceeds the upper limit of condition (2), spherical aberration is undercorrected, spool-shape distortion becomes larger, and field curvature is undercorrected.
- Condition (3) specifies the magnification of the relay finder optical system 20 so as not to further complicate the structure thereof, and so as not to further increase the size of the camera.
- the relay finder optical system 20 becomes higher so that m exceeds the lower limit of condition (3), the relay finder optical system 20 becomes larger. As a result, the Lupe (magnifying) optical systems 30 also becomes larger.
- the relay finder optical system 20 If the magnification of the relay finder optical system 20 becomes lower so that m exceeds the upper limit of condition (3), the relay finder optical system 20 and the camera can be miniaturized. However, due to an increase of the finder magnification, the focal length of the Lupe (magnifying) optical systems 30 is made shorter, so that the eye-relief becomes shorter. Consequently, the diameter of the Lupe (magnifying) optical systems 30 undesirably becomes larger, and the lens arrangement of the relay finder optical system 20 becomes complicated.
- y designates the image height
- the two types of dotted lines respectively indicate magnification with respect to the g and C lines; however, the d line as the base line coincides with the ordinate.
- y designates the image height
- S designates the sagittal image
- M designates the meridional image.
- y designates the image height the secondary imaging plane 27 .
- y designates the image height the secondary imaging plane 27 ; and the solid line and the four types of dotted lines respectively indicate spherical aberrations with respect to the d, g, C, F and e lines.
- Fe designates the effective f-number
- f designates the focal length of the relay finder optical system
- W designates the half angle-of-view (°)
- fB designates the back focal distance (the distance from the most photographer's-eye side surface of the relay finder optical system 20 to the secondary imaging plane 27 )
- Y designates the image height at the secondary imaging plane 27
- r designates the radius of curvature
- d designates the lens-element thickness or a distance between lens elements (lens groups) which is variable upon zooming
- N d designates the refractive index of the d-line
- v designates the Abbe number.
- c designates a curvature of the aspherical vertex (1/r);
- y designates a distance from the optical axis
- a 4 designates a fourth-order aspherical coefficient
- a 6 designates a sixth-order aspherical coefficient
- a 8 designates a eighth-order aspherical coefficient
- a 10 designates a tenth-order aspherical coefficient.
- FIG. 1 is the lens arrangement of the relay finder optical system according to the first embodiment of the present invention.
- FIGS. 2A through 2D show aberrations occurred in the lens arrangement shown in FIG. 1 .
- FIGS. 3A through 3H show transverse aberrations (coma) occurred in the lens arrangement shown in FIG. 1 .
- Table 1 shows the numerical data of the first embodiment.
- surface No. 1 designates the primary imaging plane 12 .
- FIG. 4 is the lens arrangement of the relay finder optical system according to the second embodiment of the present invention.
- FIGS. 5A through 5D show aberrations occurred in the lens arrangement shown in FIG. 4 .
- FIGS. 6A through 6H show transverse aberrations (coma) occurred in the lens arrangement shown in FIG. 4 .
- Table 2 shows the numerical data of the second embodiment.
- surface No. 1 designates the primary imaging plane 12 .
- FIG. 7 is the lens arrangement of the relay finder optical system according to the third embodiment of the present invention.
- FIGS. 8A through 8D show aberrations occurred in the lens arrangement shown in FIG. 7 .
- FIGS. 9A through 9H show transverse aberrations (coma) occurred in the lens arrangement shown in FIG. 9 .
- Table 3 shows the numerical data of the third embodiment.
- surface No. 1 designates the primary imaging plane 12 .
- the first through third embodiments satisfy conditions (1) through (3). Furthermore, as can be understood from the aberration diagrams and the lateral aberration diagrams, the various aberrations are adequately corrected.
- a relay finder optical system for an SLR camera with the following features can be obtained, while securing a necessary eye relief, an apparent visual angle, and a finder magnification:
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Astronomy & Astrophysics (AREA)
- Lenses (AREA)
- Viewfinders (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2007072636A JP4979421B2 (ja) | 2007-03-20 | 2007-03-20 | 一眼レフカメラのリレー式ファインダ光学系 |
JP2007-072636 | 2007-03-20 |
Publications (2)
Publication Number | Publication Date |
---|---|
US20080232791A1 US20080232791A1 (en) | 2008-09-25 |
US7761005B2 true US7761005B2 (en) | 2010-07-20 |
Family
ID=39774802
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/050,328 Expired - Fee Related US7761005B2 (en) | 2007-03-20 | 2008-03-18 | Relay finder optical system of an single-lens reflex camera |
Country Status (2)
Country | Link |
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US (1) | US7761005B2 (ja) |
JP (1) | JP4979421B2 (ja) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN106199918B (zh) * | 2016-08-31 | 2018-10-16 | 浙江舜宇光学有限公司 | 摄像镜头 |
Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4047222A (en) * | 1976-01-13 | 1977-09-06 | Optigon Research & Development Corporation | Camera viewfinding system |
US4171888A (en) * | 1977-02-28 | 1979-10-23 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system for a single lens reflex camera |
US5749008A (en) * | 1996-01-18 | 1998-05-05 | Minolta | Eyepiece |
JPH11133298A (ja) | 1997-10-29 | 1999-05-21 | Olympus Optical Co Ltd | 二次結像式ファインダー |
US20010003495A1 (en) | 1999-12-08 | 2001-06-14 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system |
JP2001290087A (ja) | 2000-04-06 | 2001-10-19 | Asahi Optical Co Ltd | 一眼レフカメラのファインダ光学系 |
US20020051300A1 (en) * | 2000-09-05 | 2002-05-02 | Nikon Corporation | Eyepiece lens |
US20020136552A1 (en) | 2001-03-21 | 2002-09-26 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system and camera having finder optical system |
JP2003121760A (ja) | 2001-10-19 | 2003-04-23 | Pentax Corp | 接眼レンズ系 |
US20050128577A1 (en) | 1999-11-09 | 2005-06-16 | Pentax Corporation | Real-image finder optical system |
US20060147200A1 (en) | 2005-01-05 | 2006-07-06 | Pentax Corporation | Digital single-lens reflex camera |
US20070172226A1 (en) | 2006-01-25 | 2007-07-26 | Pentax Corporation | Digital single-lens reflex camera |
-
2007
- 2007-03-20 JP JP2007072636A patent/JP4979421B2/ja not_active Expired - Fee Related
-
2008
- 2008-03-18 US US12/050,328 patent/US7761005B2/en not_active Expired - Fee Related
Patent Citations (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4047222A (en) * | 1976-01-13 | 1977-09-06 | Optigon Research & Development Corporation | Camera viewfinding system |
US4171888A (en) * | 1977-02-28 | 1979-10-23 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system for a single lens reflex camera |
US5749008A (en) * | 1996-01-18 | 1998-05-05 | Minolta | Eyepiece |
JPH11133298A (ja) | 1997-10-29 | 1999-05-21 | Olympus Optical Co Ltd | 二次結像式ファインダー |
US6018416A (en) | 1997-10-29 | 2000-01-25 | Olympus Optical Co., Ltd. | Secondary image formation type view finder |
US6233097B1 (en) | 1997-10-29 | 2001-05-15 | Olympus Optical Co., Ltd. | Secondary image formation type view finder including two half mirrors |
US20050128577A1 (en) | 1999-11-09 | 2005-06-16 | Pentax Corporation | Real-image finder optical system |
US20060023303A1 (en) | 1999-11-09 | 2006-02-02 | Pentax Corporation | Real-image finder optical system |
US20010003495A1 (en) | 1999-12-08 | 2001-06-14 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system |
JP2001290087A (ja) | 2000-04-06 | 2001-10-19 | Asahi Optical Co Ltd | 一眼レフカメラのファインダ光学系 |
US20010041071A1 (en) * | 2000-04-06 | 2001-11-15 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system |
US20020051300A1 (en) * | 2000-09-05 | 2002-05-02 | Nikon Corporation | Eyepiece lens |
US20020136552A1 (en) | 2001-03-21 | 2002-09-26 | Asahi Kogaku Kogyo Kabushiki Kaisha | Finder optical system and camera having finder optical system |
JP2003121760A (ja) | 2001-10-19 | 2003-04-23 | Pentax Corp | 接眼レンズ系 |
US20060147200A1 (en) | 2005-01-05 | 2006-07-06 | Pentax Corporation | Digital single-lens reflex camera |
US20070172226A1 (en) | 2006-01-25 | 2007-07-26 | Pentax Corporation | Digital single-lens reflex camera |
Non-Patent Citations (3)
Title |
---|
English language Abstract of JP 11-133298, May 21, 1999. |
English language Abstract of JP 2001-290087, Oct. 19, 2001. |
English language Abstract of JP 2003-121760, Apr. 23, 2003. |
Also Published As
Publication number | Publication date |
---|---|
JP2008233514A (ja) | 2008-10-02 |
JP4979421B2 (ja) | 2012-07-18 |
US20080232791A1 (en) | 2008-09-25 |
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